Dynamics of ovarian structures after aplication of Suprelorin® (4.7 mg de-slorelin acetate) implant for estrus induction in bitches

Abstract

The sexual cycle and ovulation in bitches occur much less often than in other domestic animals, as they are monoestrous. In addition, dogs have spontaneous ovulation and, consequently, a spontaneous luteal phase. This physiology of the sexual cycle in bitches leads to specific difficulties with reproduction. Owners often cannot connect a bitch with a dog in time and, accordingly, get offspring due to the absence of heat or prolonged anestrus. Therefore, the stimulation of the sexual cycle in bitches is gaining more and more interest among animal owners. Understanding the physiology of the sexual cycle and its stages makes it possible to manipulate it safely and without negative consequences for the bitch's body. We recommend using the Suprelorin implant in late anestrus to induce estrus and obtain ovulation in bitches. Implant Suprelorin®, primarily registered for the pharmacological sterilization of dogs and cats, causes estrus at the beginning of its action. This mechanism of action of Deslorelin implants is known as the flare effect due to its stimulating effect on the secretion of gonadotropin (GnRH), which triggers the synthesis of follicle-stimulating and luteinizing hormones from the pituitary gland. Our results showed that the use of the Suprelorin® implant (4.7 mg Deslorelin) is safe for the induction of oestrus in bitches and does not cause side effects. The proposed induction scheme makes it possible to achieve the highest level of initiation of the sexual cycle (hypothalamus-pituitary-gonads), which is as close as possible to the natural sexual cycle regarding the mechanism of action and is safe for the bitch's body. Ultrasound diagnostics occupy an essential place in studying animals with gynecological problems. There are not many studies in bitches that would show the dynamics of ovarian follicles after using the Deslorelin implant. In our studies, ultrasonographic examination of ovarian structures revealed a faster appearance of follicles in the group of bitches treated with the Deslorelin implant (4.7 mg) compared to the control group; at the same time, their size was significantly more extensive, and the ovulated faster. The appearance of anechoic structures on the ovaries with a size of more than 3 mm (mean 3.2 ± 0.1) was detected already on the third day after the introduction of the implant in 3/6 bitches in the experimental group, while in the control group, only on the fifth day (4/6) and on the seventh (2/6) day. Follicle sizes differed statistically between groups from the 9th to the 12th day. In the experimental group, the appearance of follicles was noted earlier than in the control group (starting from the third day); they were significantly more extensive and ovulated on the 14th day, while in the control group, only on the 16th day.